We test our sea vegetables annually following each harvest season and throughout the year to ensure they're free of food pathogens and dangerous levels of naturally occurring or human origin contaminants such as heavy metals, pesticides, petroleum residues, and radiation.  Annual test results are posted below.

Why We Test

Although our sea vegetables are mostly harvested from wild and remote reaches in the Gulf of Maine and the North Atlantic, we can’t control what the ocean currents may carry and the winds may deposit. And even though seaweeds have been safely consumed for centuries, we want to make sure this continues to be true today.

What We Test For


Our products are regularly screened for total bacterial counts; coliform bacteria and pathogenic E. coli; foodborne pathogens such as Salmonella and Staphylococcus aureus; and mold & yeasts. Microbial test results aren't posted on the website for the simple reason that if we found harmful microbes in any one of our products, we wouldn’t sell it! Because dried sea vegetables contain natural sea salts and have very little moisture, they are inhospitable for bacteria and they have an extended shelf life. Microbial testing is done annually and repeated throughout the year for popular products.

Maine Coast Sea Vegetables - water activity testing of seaweed
We periodically test for water activity and moisture in many of our sea vegetables to assess microbial viability.


Widely used in agriculture and by property owners, these compounds are of concern because they can appear as residues on foods. We use a screening protocol endorsed by the USDA National Organic Program (NOP) for ensuring produce meets the ‘certified organic’ standard for pesticide and herbicide residues. This testing is done annually by us and at random by our certifying agency (OCIA); our test results are posted below as NOP panel.

Petroleum Residues

Referred to as Polychlorinated Aromatic Hydrocarbons (PAHs). This screen verifies our seaweed is free of gasoline and oil residues coming from surface runoff or boats. This testing is done annually and the results are posted below as PAH's.

Heavy Metals

Our labs use gas chromatography and mass spectrometry to detect and quantify trace levels (<1 part per million) of cadmium, lead, mercury, and inorganic forms of arsenic in our seaweed. These elements are widely distributed in the world’s oceans from both natural and manmade sources. This testing is done annually and the results along with more detail on heavy metals in seaweed are posted below.


Following the 2011 Fukushima nuclear catastrophe, customers became concerned that even seaweed as far away from the disaster as Maine could have become contaminated, and we’ve been annually testing ever since.  Test results can be found below. 

How We Test

Testing is done every winter after the harvest has been dried and stored. We take care to collect composite samples representative of each species, growing area, and form (leaf or milled). We don’t test every single product each year, but we do test a representative of every species and growing area. For example, we may test dulse flakes but not powdered dulse, because the two products come from the same species and area. In this case, test results for dulse flakes can be applied to the powdered form.

Testing is done through accredited third-party labs. It’s important to understand the nature and substance of seaweed to accurately analyze it. Our contract labs use analytical methods refined over many decades by scientists from around the world, and they're validated by the EPA, FDA and global certification organizations before being approved for food testing. We work closely with our testing labs to  remain current with the latest changes and refinements to test methods. Some of our testing labs include: Katahdin Analytical, Northeast Laboratories, Brooks Applied Labs, and eurofins.


Seaweed is a traditional whole food that's  been eaten by people  around the world for many thousands of years with healthy results. However, every person is unique and we are unable to predict your body's response. There may be elements of these plants not suitable for your particular biochemistry or condition. Only you can determine what's best for you, in consultation with your healthcare practitioner. The seaweeds we sell are wild harvested, uncultivated marine algae. Naturally occurring fluctuations in the sea plants occur due to season, climate, tidal flow and time of harvest. The information we present on this website is believed to be accurate and reliable, but the testing is not carried out by Maine Coast Sea Vegetables — it represents composite averages — and it is not guaranteed as a condition of sale. Maine Coast Sea Vegetables makes no warranty, either express or implied, and assumes no liability for this information or the products described.

Table of 2019-20 Test Results
Species & Product Info Inorganic Arsenic
(>0.02 ppm)
(>0.05 ppm)
NOP Panel
(>0.01 ppm)
Alaria Leaf
Alaria esculenta
0.09 2.01 0.03 U U U
Alaria Granules
Alaria esculenta
0.09 2.4 0.28 U U U
Bladderwrack Leaf
Fucus vesiculosis
0.19 1.07 0.19 U U U
Bladderwrack Granules
Fucus vesiculosis
0.32 1.26 0.9 U U U
Dulse Leaf
Palmaria palmata
0.02 0.73 0.21 U U U
Dulse Flakes
Palamaria palmata
0.08 0.45 0.21 U U U
Irish Moss Coarse
Chondrus crispus
0.39 0.43 0.82 U U U
Sugar Kelp Leaf
Saccharina latissima
<0.1 1.9 0.11 U U U
Laver Leaf
Porphyra umbilcalis
<0.09 4.04 0.1 U U U
Rockweed leaf
Ascophyllum nodosum
0.08 0.46 0.38 U U U
Rockwed Granules
Ascophyllum nodosum
0.12 0.42 0.24 U U U
Raw Nori Sheets
Porphyra yezoensis
<0.08 3.18 0.11 U U N/A

U = Undetected above method detection limit or 0.05 ppm; ppm = parts per million, equivalent to micrograms per gram, or milligrams per kilogram 

Heavy Metals in Seaweed

Customers may wonder why we choose to test our Certified Organic sea vegetables for heavy metals, or why some of our products bear a "Proposition 65" warning about lead and cadmium.  The reason for both is that seaweed is highly effective at bioaccumulating minerals, metals and other elements from seawater.  In addition to accumulating essential mineral nutrients, seaweed also accumulates certain heavy metals that are harmful when the body absorbs them in excess.

Metals occur naturally in the ocean due to weathering of the earth’s crust. These metals are widely disbursed, even in the remote and wild areas where our seaweed is harvested far from big cities and industry.  Although Organic Certification ensures our seaweed isn't harvested near local sources of contamination such as boat marinas or municipal outfalls, it can't guarantee purity.

Because we know that heavy metals are likely to be found in seaweed, we test to verify they're not present above harmful levels. We disclose the test results so that customers can make an informed choice based on their own unique health needs and perception of risk.  We ourselves frequently enjoy eating sea vegetables (often every day!) because we believe their many health and nutrition benefits far outweigh any risk posed by the low levels of heavy metals they contain.  Scientists have studied this topic for many years. This research establishes safety thresholds for heavy metals based on consumption patterns, examines the question of bioavailabilty (not everything we eat is absorbed), and describes how seaweed is used for bioremediation because it contains polysaccharides that chelate (bind to) heavy metals, which is why some say it can be eaten to detoxify heavy metals. For more detail on what we've learned please see the FAQ about Heavy Metals in the section about environmental concerns.

Radioactivity Testing in Seaweed

We began testing our seaweed for radioactivity in 2011 in response to the Fukushima, Japan nuclear catastrophe, and we haven't stopped since. Humans have released radiation into the environment, whether intentionally or accidentally, ever since the US first tested atomic bombs in 1945. Because eating seaweed offers some protection from radiation, it’s important to ensure the seaweed itself is free of harmful radioactive isotopes.  This topic is further addressed in our FAQs.

The lab of Professor Thomas Hess, University of Maine Department of Physics, tested our seaweed every year from 2011 to 2018.  A summary of the test method and results, as well as how to interpret the results, can be found here in this downloadable PDF "Summary of Radiation Testing 2011-2019".  In 2020 we moved to using a commercial lab for this testing.  Our most recent results are shown below.

Sea Vegetable Activity in Cesium 134 Activity in Cesium 137 Activity in Iodine 131
Alaria Leaf <1.0 Bq/kg <1.0 Bq/kg <2.0 Bq/kg
Dulse Leaf <1.0 Bq/kg <1.0 Bq/kg <2.0 Bq/kg
Fucus Granules <1.0 Bq/kg <1.0 Bq/kg <2.0 Bq/kg
Raw Nori Sheets (China) <1.0 Bq/kg <1.0 Bq/kg <2.0 Bq/kg

Don't use a Geiger Counter to Detect Radiation in Seaweed!

It is not recommended to use a Geiger counter to detect radiation in seaweed.  You will almost certainly get a positive result, but it does not necessarily indicate hazard. A natural (and harmless) radioactive isotope of potassium (K-40), found in seawater and most if not all land and sea plants, accounts for nearly all of the radioactivity observed in seaweeds. This can cause a false alarm if a Geiger counter is used to detect whether seaweed is “radioactive”. This link explains the issue in more detail: Geiger Counters and Sea Vegetables.

The following links provide additional resources for learning more about radiation. And of course, please feel free to contact us at info@seaveg.com with questions.